why the honorverse would be full of dead planets

An OTL example is the nuclear MAD philosophy. I can remember in the 1960s being convinced that some egotistical leader from either side would actually take the chance that a big enough early strike might knock out the other side.
Luckily for us all I was wrong (so far), but the same situation exists in the Honorverse.

How to destroy a planet:

First, there has been a discussion in this thread about what will happen with a megaton of sand in the atmosphere.

At .7c it's going to dump 3e25 joules somewhere. It's hitting 2.5e21 grams of atmosphere (Earth, for one hemisphere. To be habitable to unprotected humans this number can't vary by more than 2x in either direction so it's a reasonable proxy for all inhabited worlds.)

At constant volume (this will happen so fast that the air can't spread out) and Earthlike temperature it's about .71 J to heat a gram by a degree. Note that we have a little over 10,000 Joules per gram. We won't get the full 14,000C of heating because it will take more to heat it as it warms but that's not going to save you. The chart I'm looking at tops out at .92J/g at 1500C so a ballpark answer is it will be heated to 10,000C. Obviously, at least that hemisphere dies.

Now, as to how to carry out the strike:

As has been said by others, drop in outside detection range and boost to .7c. You want to be on the opposite side of the star from your target. Hold onto your cargo, close to about 14 light hours, aligned so your target just goes behind the star at this point. (Again, I'm assuming the Earth/Sol system, the star size and planet orbit will change this number.) Drop your cargo--which is boulders, not sand. Now fire your reaction thrusters in the direction opposite of the planet's orbit. IIRC from the battle at Cerberus we saw the ship had about 64kkm/sec of delta-v, lets say we only have half that since it's a civilian vessel and we only expend half of what we have--we are moving away from the planet at 15k km/sec, we will pass a billion km away and almost certainly not be noticed (note: we haven't used our wedge after the initial boost--no gravitic detection.) Even if we are noticed there's nothing they can do about it.

Our rockpile is of course an x-ray source in the sky--but note that it's behind the star--the planet can't see it.

The trajectory I have picked will cause the rocks to miss the star by about 1 solar diameter, in the last 3.6 hours of flight (remember, lightspeed sensors) the planet will see an x-ray source slowly emerging from behind the star--that is, if they can make it out at all as a separate entity from the star. And who points telescopes at the local star, anyway??

Once it clears the star the planet has less than 3 minutes to detect it and intercept. There is no way to match orbits, thus the only defense is to interpose a wedge. From the response to Oyster Bay we can see that this would be hopelessly inadequate in stopping a pile of rocks that are spread across the planet. They'll get some, most will get through.

Now, those numbers for the reaction thrusters bother me, they're awfully high. It doesn't even matter--even 10% of that number still puts the ship outside the range most planets can detect it and I don't think anything short of Mycroft could do anything about it.

I'm probably being way too conservative sending the rocks a solar diameter out, also. Solar heating is basically a non-factor, they would only be singed a bit no matter how close they come. The limit will be a matter of not hitting too much solar atmosphere and I don't know enough about stellar physics to figure out how close they can come.


Note that this tactic isn't viable against systems with multiple major planets but how many systems contain multiple worlds with enough population to have their own astronomical observatories?

Loren Pechtel wrote:How to destroy a planet:

[snip]

Our rockpile is of course an x-ray source in the sky--but note that it's behind the star--the planet can't see it.

The trajectory I have picked will cause the rocks to miss the star by about 1 solar diameter, in the last 3.6 hours of flight (remember, lightspeed sensors) the planet will see an x-ray source slowly emerging from behind the star--that is, if they can make it out at all as a separate entity from the star. And who points telescopes at the local star, anyway??

Once it clears the star the planet has less than 3 minutes to detect it and intercept. There is no way to match orbits, thus the only defense is to interpose a wedge. From the response to Oyster Bay we can see that this would be hopelessly inadequate in stopping a pile of rocks that are spread across the planet. They'll get some, most will get through.

So you are targetting a planet that's got enough reaction capability that you need to try to hide the relativistic attack, yet so minimal a space presence that they didn't deploy the basic solar orbit system sensors to avoid people sneaking up on them from behind the sun?
Nobody with even a basic space navy is going to rely exclusively on planetary, or planetary orbital, sensor to try and monitor the whole system. (Yes the other sensors will have a lightspeed lag to inform the planet of what they see, but even a relayed warning of a moving x-ray source 14 light hours away (20 hours from impact) should still give you a couple hours warning.

But ok, given a target that's blind to what's happening behind their own sun I guess that this attack would work - but it seems overkill to use relativistic boulders to attack such a weak system.

I'm not at all sure that getting that close to the sun won't significantly modify the trajectory of your objects just due to the solar atmosphere and heating, and in a somewhat chaotic way. And a little motion that far out might well result in a miss.

But interesting.

I think I first said it here years ago. If the MAlign thought they needed to, the Eridani Edict wouldn't stop them.

The only thing stopping them really is the public relations. Not towards them, but towards their target.

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If the Honorverse would be full of dead planets, I surmise it would be the result of wars over the limited availability of prolong. Can you imagine the wars that would ignite from everyone wanting to drink from a limited fountain of youth? It is the stuff of many Sci-Fi tales now - the lengths that one would be willing to go to achieve a fountain of youth.

I shudder to think of the global wars on Earth if the same situation existed between the varying wealth of countries who could afford prolong and those who couldn't.

I can also imagine the meltdown of our own country if prolong was a thing but unavailable across the board.

Neither am I, but in any case the Sun only subtends an angle of 30', and simple orbital mechanics says that you will get more than that in curvature of the trajectory [correct calculation at that distance is in the realm of GR, so don't have exact figure]. This is easily allowed for, of course, but means you have to be rather far from a straight line from star to planet, so the launch point will in fact be quite visible. And, since this configuration requires launching in the orbital plane of the system, which is the filthiest part of it, your ship, if it even makes it that far, will have been a very prominent source on the sky for days to weeks before that.

As for who points telescopes at the Sun? Everyone with any concern for space weather, of course, which means anyone with any space presence and a modicum of intelligence, since not even Honorverse rad shielding is going to make small craft and EVA personnel invulnerable. Which, again, means that this is going undetected only in systems where you don't need to sneak up on people. Going into orbit and flushing all your toilets in an Icey BM strike would probably do the job.

kzt wrote:I'm not at all sure that getting that close to the sun won't significantly modify the trajectory of your objects just due to the solar atmosphere and heating, and in a somewhat chaotic way. And a little motion that far out might well result in a miss.

But interesting.

Annachie wrote:I think I first said it here years ago. If the MAlign thought they needed to, the Eridani Edict wouldn't stop them.

The only thing stopping them really is the public relations. Not towards them, but towards their target.

Yes. David had them mention that.

kzt wrote:I'm not at all sure that getting that close to the sun won't significantly modify the trajectory of your objects just due to the solar atmosphere and heating, and in a somewhat chaotic way. And a little motion that far out might well result in a miss.

But interesting.

It doesn't matter. Lets say the flyby induces a 100 m/s unexpected lateral deviation. (There will be a slight bending due to gravity but that is anticipated.) NASA would really care about that but the attacker wouldn't. The rocks have 12 minutes left at that point--100 m/s translates to a 72km deviation from the aim point.

However, I would be surprised at even 1 m/s lateral deviation--there simply won't be much time for anything to shove it sideways. There will be unpredictable drag that will slow them ever so slightly but they'll still be heading at the target. Lets say they're slowed by 1 km/sec. The rock arrives 3 ms late, the planet moves 90 meters in that time.

Louis R wrote:Neither am I, but in any case the Sun only subtends an angle of 30', and simple orbital mechanics says that you will get more than that in curvature of the trajectory [correct calculation at that distance is in the realm of GR, so don't have exact figure]. This is easily allowed for, of course, but means you have to be rather far from a straight line from star to planet, so the launch point will in fact be quite visible. And, since this configuration requires launching in the orbital plane of the system, which is the filthiest part of it, your ship, if it even makes it that far, will have been a very prominent source on the sky for days to weeks before that.

I don't follow your logic as to the degree of turn. The surface gravity of the sun is 274 m/s^2. My calculus is far too rusty so I'll make a simplification: All the deflection happens while the rock is within 5 diameters of the star, but it's at the full surface gravity. (Note that this greatly overstates the answer.) That's 11 mkm, 37 seconds. 274 m/s^2 * 37 seconds = 10.1 km/s. A 20,000th of it's velocity. To get a 30 degree deflection this would have to be half it's velocity.

As for who points telescopes at the Sun? Everyone with any concern for space weather, of course, which means anyone with any space presence and a modicum of intelligence, since not even Honorverse rad shielding is going to make small craft and EVA personnel invulnerable. Which, again, means that this is going undetected only in systems where you don't need to sneak up on people. Going into orbit and flushing all your toilets in an Icey BM strike would probably do the job.

But they won't be x-ray telescopes. I'm sure the space weather equipment will pick this up, just not in time to sound the alarm.